Chromatography...Oh Yeah!

Transcription

1 Chromatography...Oh Yeah! What s In Kool-Aid? An Introduction to Extraction and Chromatography OVERVIEW: The purpose of the experiment is to separate and analyze the components of prepared Kool- Aid using a solid phase extraction (SPE) column. OBJECTIVES: Before doing this lab you should understand: The concept of a mixture. The concept of a solution. The difference between a homogenous mixture (i.e. a solution) and a heterogeneous mixture. After doing this lab you should be able to: Explain the concept of extraction and how it relates to environmental analysis. Explain the difference between chromatography and filtration. Separate the components of a given solution based on polarity. INTRODUCTION: Extraction is a technique commonly used in many areas of chemistry and biology, particularly in environmental analysis. It is one of many techniques used to remove certain chemicals from a mixture. This isolation is done to purify the desired chemical or to separate it so that it can be identified or studied. Extraction is often the first step done when a chemist wishes to identify a chemical, determine its structure, and possibly synthesize it. For example, artificial vanilla exists because the natural chemical was isolated from a plant, and its structure was determined. Once the structure was known, a procedure for producing it less expensively in the laboratory was developed. Pollutants in soil or water are often dissolved in the environmental sample and must be extracted out to determine how much is there and if there is enough there to cause harm to humans or wildlife. For many of these applications, filtration is not effective because the desired components are dissolved in the sample material. Filtration is effective for removing particles or other un-dissolved components of a heterogeneous mixture, but means other than physical separation are needed to separate out desired dissolved components. UC San Diego Pg 1

2 C-18 Silica SPE Bead Structure Solid phase extraction (SPE) will be used for this procedure. Very small silica beads covered with a material called C-18 (18 carbon atoms bonded together) are packed in the column. C18 Chain Silica Bead When a mixture is passed through the column, some components are more powerfully attracted to the C-18 material than others. These components "stick" to the column and are held while the other components pass through. By selecting proper solvents, the materials adhered to the column can be removed and isolated for further study. SPE Column Long End } C18 Packing MATERIALS: SOLUTIONS: C-18 SPE column Kool-aid solution 8 test tubes Isopropanol (5%, 10%, 20%, 70%) 10 ml syringe DI water Colored pencils (optional) SAFETY: Always wear safety glasses in the lab - isopropanol solutions are flammable and could splash! Use equipment only as directed. Never eat or drink in the lab. UC San Diego Pg 2

3 PRE-LAB QUESTIONS: 1. Explain the difference between chromatography extraction and filtration. 2. Which technique from #1 is used in this lab? 3. Explain the difference between a homogenous mixture and a heterogeneous mixture. 4. Look up the following words or concepts in the lab handout introduction: a. Polarity b. Extraction c. Dissolved d. Solid phase extraction e. Effluent UC San Diego Pg 3

4 f. Conditioning a column g. Solvent 5. Using the line below, rate the relative polarity of the solvents used in the Kool-Aid lab: 100% isopropanol, water, 5% isopropanol, 10% isopropanol, 20% isopropanol. Write the solvent names above the line, in the order and place they should be in based on their relative polarity. Polar Non-Polar 6. Identify the following about hexane (circle choices): Bonds: polar or non-polar or both C18 Column Circle any polar bonds on the molecule. Whole molecule: polar or non-polar 7. Identify the following about isopropanol (circle choices): UC San Diego Pg 4

5 Isopropanol Bonds: polar or non-polar or both Circle any polar bonds on the molecule. Whole molecule: polar or non-polar 8. Assign the roles for your group members and record them here: a. Data Recorder Records all data and observations in the data table page of your lab handout. i. Name: b. Solution Adder Adds the solutions to the top of the column with a syringe. i. Name: c. Solution Manager Prepares and gives solution tubes to Solution Adder; Keeps track of what solution to add next by following the procedure. i. Name: d. Column Manager Keeps the column in proper position and over the correct tube number; Pushes the solutions through the column with the plunger after the Solution Adder has added them. i. Name: UC San Diego Pg 5

6 PROCEDURE: Label test tubes in the following order: Go through the following steps to add the solutions in the table (IN THIS ORDER) to the column and collect the effluent from each step in a different test tube. STEPS FOR EACH SOLUTION/TUBE: 1. Place the first tube underneath the column. 2. Fill the 10mL syringe. 3. Attach the tip of the syringe into long end of the column. 4. Slowly push through with the syringe (See demonstration). 5. Remove the syringe. Tube Order Tube Solution Added 1 70% 70% isopropyl alcohol 2 Water Water 3 Kool-Aid Kool-Aid 4 Water Water 5 5% 5% isopropyl alcohol 6 10% 10% isopropyl alcohol 7 20% 20% isopropyl alcohol 8 70% 70% isopropyl alcohol 6. Record the colors of the effluent and the column on the data table for each step. TEST FOR SUGAR: 1. Decide as a group which tubes would be the most likely to contain sugar: 2. Dip the test strip in your test tube and wait 30 seconds for the color to develop. Tip 3. Compare strip color to the chart below for relative sugar concentrations. Long End UC San Diego Pg 6

7 RECORD YOUR DATA BELOW UC San Diego Pg 7

8 CLASS COMPARISON DATA Use this sheet to record the other groups data. Illustrate the changes they observed in the color of the column and effluent AND where the glucose strip test was positive. Kool-Aid: _Cherry Kool-Aid: _Grape UC San Diego Pg 8

9 Kool-Aid: Orange Kool-Aid: _Lemon-Lime UC San Diego Pg 9

10 Name Essay for Kool-Aid Lab Due: Describe (in words, or pictures, or both) what would happen if we mixed all three flavors of Kool-Aid solutions (Cherry, Orange, Grape) and ran them through our column extraction system. Be very specific in regards to the changing color of the column and effluent when the different polarity solvents are added. You should think about the different dyes involved and glucose and their relative polarities in relation to the order that they come off of the column. UC San Diego Pg 10

11 Name POST-LAB QUESTIONS: 1. Were there any differences between the other groups results and your own? If so, what were they and why might they have gotten different results? 2. Did your Kool-Aid samples contain any of the same dyes? Explain. 3. Which dye had the highest affinity (attraction, stickiness ) to the column? Explain. UC San Diego Pg 11

12 Name 4. If two different colors both came through using 10% isopropyl alcohol, how would you change the extraction to make these separate? 5. Could this same lab activity be performed on other types of solutions or to separate out different components? Why or why not? UC San Diego Pg 12